1. Field of the Invention
This invention relates to a process for the reception of a binary digital signal, which may also exhibit phase shifts, and it relates, more particularly, to an arrangement including elements having an approximately constant propagation delay, operating at a clock whose frequency is equal to or plesiochronous with the bit rate of the digital signal and whose phase difference is selected arbitrarily with respect to the digital signal.
2. Description of the Prior Art
A circuit arrangement for the regeneration and synchronization of a digital signal, which compensates for the phase oscillations of the incoming signal bits, is already known from German patent document DE 34 31 501 A1. For that purpose, it contains a series circuit consisting of a controllable delay line coupled to a delay control unit, to which the controllable delay line is connected through address lines. The decision logic is supplied over a clock line with a system clock whose frequency corresponds to the bit rate of the digital signal that is to be regenerated and synchronized.
In an ideal binary digital signal, the rising and falling edges of each binary digit lie within a fixed pattern, which is determined by the period of the clock frequency. Any deviation of the edges from this pattern is referred to as jitter. Within defined limits, this jitter must not result in information errors when the signal is received.
Two different kinds of jitter can be distinguished. The first consists of time deviations of two successive edges from the prescribed raster, the second of slowly developing phase shifts, which can lead to a time shift of more than one period.
FIG. 1 shows a period T of the clock frequency, with a permissible jitter range -x and +x for the pulse transitions or edges. For a delay-free phase equalization, only one edge can be the reference point for the arrival of a new pulse of the digital signal. If this occurs, in accordance with FIG. 2, at the time t2, then a half-period T/2 of the clock frequency must elapse before the pulse is received at time t4. The deviations that can occur in the determination of the time T/2 are taken into account by the time intervals + y and - y.
If the edge arrives at time t3, then reception is possible only when EQU T/2+ y&lt;T-2x. (1)
On the other hand, if the edge arrives at time t1, then perfect reception requires that EQU T/2- y&gt;2x. (2)